A newly released report commissioned by Canada's energy regulator has concluded that clean-up efforts for an offshore oil spill in the Arctic could be impossible at least one day in five because of bad weather or sea ice.

And a spokesman for one environmental group said that a recent U.S. study suggests even that figure could be underestimating the risk.

"They may be overly optimistic," said Rob Powell of the World Wildlife Fund's Arctic program.

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As part of its ongoing review of regulations that will eventually govern energy development in Canada's North, the National Energy Board commissioned an environmental consultant to study how typical spill clean-up methods would be affected by likely conditions in the Beaufort Sea and Davis Strait.

Winds higher than 10 metres per second, for example, make it impossible to burn oil slicks, one of the main methods used to clean up ocean spills. Dispersants, which break up the slicks, are of little use in waves higher than three metres.

Booms and skimmers, which contain and remove the oil, are only marginally effective in water that is more than 10 per cent ice-covered. Aircraft, essential to direct any clean-up operations, need at least a kilometre of visibility.

S.L. Ross Environmental Research took those limits and compared them to actual Arctic conditions during the open-water season, based on 20 years' worth of weather data. That report was posted in mid-July.

The company found that in the Beaufort Sea, even in June – the most favourable month – weather and ocean conditions would prevent any of those three clean-up methods from being used about 20 per cent of the time. Conditions deteriorate over the summer until October, when clean-up would be impossible 65 per cent of the time.

In the central Davis Strait, July conditions would block clean-up 27 per cent of the time. By November, that worsens to 80 per cent.

The report points out that weather changes rapidly in the North, and impossible conditions one day may be favourable the next. As well, oil spilled in one season can be cleaned up the next.

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But delays can make cleanup harder as the oil weathers or emulsifies with seawater, the report says.

Several energy majors have already purchased exploration rights in the Beaufort Sea. Drilling has already begun on Greenland's side of the Davis Strait.

Mr. Powell said it's important this kind of research is conducted before Canada approves any more activity.

"We're pleased to see that it has been done," he said.

However, he points out that even when conditions for clean-up are good, the best available technology still isn't very effective.

"The number that really matters is the fraction of oil that can be recovered from the environment," he said.

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Mr. Powell said data from the clean-up of last year's spill in the Gulf of Mexico suggested that even under the best conditions, skimmers left behind 80 per cent of the spill.

As well, the U.S. Geological Survey, which is also considering Arctic drilling, found dispersants may not be that effective.

"Substantial scientific and technical work as outlined by various expert groups still must be done before dispersants can be considered a practical response tool for the Arctic," the survey concluded.

The survey also expressed concern about the toxicity of chemicals used to aid the burning of oil slicks.

Mr. Powell said any Arctic offshore drilling should be approached with caution.

"Our reading is that oil spills into the Arctic environment in any quantity cannot be recovered with the means currently available. It's kind of like unscrambling an egg."

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